Block Thread Repair

Thu Aug 01, 2013 1:22 pm

Well, I finally got the stud out of the block and the hole tapped out. I'm reasonably certain that the last time that engine was worked on - this stud was also and issue. While the stud screws into the block now - the threads are not sharp with some play in the stud whilst in the hole. There is some concern I won't be able to properly torque this one bolt. Questions below.

1. Can the JB Weld trick be used to repair these threads, whereby the stud is inserted oiled with JB Weld in the hole - tile it cures?2. Is the better fix to drill and tap it to the next fractional size larger in the head and the block?3. Should I put the head on and test to see if the remaining threads will take the torque - I'm concerned this could lead to stripping the block.4. Is there another approach?

I was reluctant to place this post under the extraction process thread as that issue is NOW solved.

Ken

Re: Block Thread Repair

Thu Aug 01, 2013 1:55 pm

Use a helicoil. That is a standard repair for such issues in BIG engines.

Al

Re: Block Thread Repair

Thu Aug 01, 2013 3:45 pm

Ken,

Every head bolt on my '53 is Heli-Coiled. The recommended torque on these bolts is high, don't remember the torque spec., When I stripped out one hole and felt another one starting to, I stopped and Heli-Coiled all of them. I used a sealer on the threads and let them set up prior to installing the head.

I think the Heli-Coil installation would be your best bet for a good fix.

Rick

Re: Block Thread Repair

Thu Aug 01, 2013 4:14 pm

Same answer! Ed

Re: Block Thread Repair

Thu Aug 01, 2013 8:34 pm

ScottyD'sdad wrote:Same answer! Ed

Ed - Ricky - Do I need a drill press big enough to drill them out or can it be done with the 25/64" bit in a hand drill?

Glad that I've had 3 replies and all agree.

Re: Block Thread Repair

Thu Aug 01, 2013 9:06 pm

You can drill it out with a hand drill. Heli-Coil will specifiy a drill bit size an provide a tap the correct size for the inserts. You can buy a kit that has the drill, tap several coils and an insertion tool. They can be pricey so you might check with some area auto parts stores that loan tools, you might get lucky and find someone that will loan you the tools. You can trim the coils to length if you need to. There are other types of inserts that don't require a special size tap like Heli-Coil does. You'll need to do a little research to see if that is a good possible option too.

Re: Block Thread Repair

Thu Aug 01, 2013 9:56 pm

there are other companies than Helicoil that sell the same type kit, do not get hung up on the brand name. You said studs, if you were referring to the head and not the manifold, it uses cap screws originally.

Re: Block Thread Repair

Thu Aug 01, 2013 10:52 pm

Drilling and tapping for the coil insert involves removing the least amount of material from the engine block of all the inserts available. It is my first choice by far.

Re: Block Thread Repair

Fri Aug 02, 2013 5:25 am

As always do as you feel is best. When repairing stripped threads consider using TimeSerts (www.timesert.com) in lieu of Heli Coils, they're solid metal not a spring. Although more costly I believe they make for a better repair. On all remaining threaded holes throughtly clean and chase them with the correct size thread restorer (not taps they're for cutting new threads). I use anti-seize on all of my threaded fasterers.

Re: Block Thread Repair

Fri Aug 02, 2013 5:52 am

John *.?-!.* cub owner wrote:there are other companies than Helicoil that sell the same type kit, do not get hung up on the brand name. You said studs, if you were referring to the head and not the manifold, it uses cap screws originally.

My Bad John - it was the 3/8 - 16 Bolt that was busted off in the head.

Re: Block Thread Repair

Fri Aug 02, 2013 6:26 am

I have a question about this. If you are thinking of over drilling for a Heli Coil, why wouldnt you just drill out to the next fractional size and tap the hole, or maybe even just run the next larger tap in the existing hole? It seems to me that this would remove the least amount of material. Just a thought.ThanksBill

Re: Block Thread Repair

Fri Aug 02, 2013 9:12 am

gitractorman wrote:...... why wouldnt you just drill out to the next fractional size and tap the hole, or maybe even just run the next larger tap in the existing hole? It seems to me that this would remove the least amount of material. Just a thought.ThanksBill

Actually the helicoil removes a little less material, plus you do not need to drill the head oversize then have one odd size bolt in the mix.

PVF, those original bolts were grade 9. Grade 8 is right at it's limit when torquing to 45 ftlb. Just a caution when replacing.

Re: Block Thread Repair

Fri Aug 02, 2013 9:38 am

Bus Driver wrote:Drilling and tapping for the coil insert involves removing the least amount of material from the engine block of all the inserts available. It is my first choice by far.

As always, Bus Driver is giving good advice. Start with the method that removes the least of the original material. If it fails, you have other options. Properly installed Helicoils rarely fail.

Drilling/tapping to the next size leaves you with the question of what is the next step. Do you use a bigger bolt? If so, how do you torque the head down? . . .

Solid inserts require a larger hole/thread than a Helicoil. Many of them require a 2 size increase, i.e. a 3/8 insert requires a 1/2 outer thread. Based on the chart on the Timesert page, they have their own taps, about a size and a half up from the size you are repairing. Save the solid inserts for if a Helicoil fails.

Re: Block Thread Repair

Fri Aug 02, 2013 9:58 am

Thanks everyone - I want to remove the least amount of material from the block as possible - Bus Driver stated - confirmed by others.

Re: Block Thread Repair

Fri Aug 02, 2013 6:17 pm

Ken:

HeliCoil is the best choice. I have done a couple dozen now and they are not as hard as I thought. I hope you ordered extra inserts -- you WILL need them - 3/8"-16 is pretty common on the Cub plus you get free shipping over $25.00

ReCoil inserts are basically identical to HeliCoil (the name brand) but can be purchased a bit cheaper on the net. There are a few others I think, but ReCoil and HeliCoil are the two best. I get the NAPA Balkamp taps to make bottoming taps as they are about half the price or more than HeliCoil (name brand) kits I get at my local supply house. ReCoil is Alcoa which was new to me, so both Emhart and Alcoa are US based.

When it comes to freehand drilling in materials in my trade I have no qualms at all, but when I am freehand drilling in cast like a final or the block, I would much prefer a drill press or if that is impractical a Mag Drill and a broach. That way it is guaranteed to be perpendicular to the deck. I am terrified of drilling slightly off perpendicular as that would really affect how the head bolts will torque down. I may be frettin for nuttin .. but thems the thoughts that run through my cranium. Not all of us have access to a Mag Drill or a Bridgeport. Be nice ifn we did. Wish you luck

Nice thing about this thread is that is has allowed me to relocate my missing bookmarks